1. Field of the Invention
The present invention relates to a method and apparatus for improved diagnosis of breast tumors using computer vision and neural network image processing.
2. Description of the Background Art
The demand for screening mammography has substantially increased in the last 10 years. For example, the Mayo Clinic has experienced an increase in volume from fewer than 10,000 mammograms in 1979 to more than 36,000 in 1989. Based on statistics maintained at the Mayo Clinic for the years 1986 to 1988, mammography failed to detect 4% of the cancers removed surgically. Malignancy was found in 25% of all surgical biopsies performed after a wire localization procedure. A benign pathologic result was noted for 75% of these patients. Further, the 4% false-negative negative rate for detecting cancer cannot be equated to sensitivity. True sensitivity can only be determined by continued follow-up with the patient.
In current radiologic practice, ultrasound is used as a tool to improve the specificity and sensitivity of total breast imaging. Sensitivity is the ability to identify malignant tumors divided by the total population of patients with the malignancy. Specificity is the ability to identify benign tumors divided by the total population of patients with benign tumors. Although both sensitivity and specificity are important, it is preferable to miscategorize patients as a false positive, rather than a false negative.
When the radiologist arrives at an indeterminate diagnosis based on the reading of a mammogram, ultrasound imaging of the lesion probably will be done as an intermediate step between mammography and biopsy if the lesion in question is a palpable mass, a mammographic mass, or both. If ultrasonography reveals a cyst, no excisional biopsy is recommended. Otherwise, if an indeterminate tumor is diagnosed, a biopsy is usually, but not always, recommended.
A cyst is a collection of liquid that usually is seen on ultrasonographic examination as a well-circumscribed lesion with no internal echoes, and increased through-transmission of sound. Cysts are considered benign lesions.
Occasionally, malignant lesions can have mainly cyst-like characteristics on ultrasonographic examination. A malignant cystic-like lesion can easily be incorrectly diagnosed as benign. The present state-of-the-art of breast ultrasound attempts to distinguish between cystic and solid lesions. However, using current ultrasonographic criteria, solid lesions are indeterminate.